Need Help Completing Loft - Surfboard Fin...

I found a STEP file of a surfboard fin, imported in to OS and have a decent strategy to recreate it using the loft feature but can't quite find a way to complete the last part of the loft creating the end of the fin. I can see an additional 4 features in the STEP solid but was wondering if there was a way to recreate the end of the fin using a less complicated and more flexible method.

Vertex matching is a pro/e thing, you can turn it off here. The vertex/point is the way to go but the point needs to be defined properly. Define a plane or face that's parallel to the fin's end:

Here I'll do it in a different model:

Changing the attitude of the point's plane, It'll effect the curvature at the crown:

To illustrate this technique further, I changed the end condition of the point sketch from normal to tangent:

In summary, when you have a point on a plane using a sketch, Onshape knows about the point because you select it as a profile. What you need to understand is that Onshape also knows about the plane the point was drawn on and also uses this in your surface definition (normal / tangent).

Thank you Billy that gives me a pretty intensive homework assignment. Curious about your first sentence, "Vertex matching is a pro/e thing, you can turn it off here." Not sure what pro/e is nor did I see where one might turn it off. Thank you again very much for taking the time to reply.

I thought lofts needed to share the same number of vertices? How would one loft from a single vertex to a profile with 4 vertices? I'll experiment but have been trying different methods for a long time and I think the techniques described are a bit over my pay grade but thanks for the replies.

Vertex matching is a pro/e thing, you can turn it off here. The vertex/point is the way to go but the point needs to be defined properly. Define a plane or face that's parallel to the fin's end:

Here I'll do it in a different model:

Changing the attitude of the point's plane, It'll effect the curvature at the crown:

To illustrate this technique further, I changed the end condition of the point sketch from normal to tangent:

In summary, when you have a point on a plane using a sketch, Onshape knows about the point because you select it as a profile. What you need to understand is that Onshape also knows about the plane the point was drawn on and also uses this in your surface definition (normal / tangent).

Thank you Billy that gives me a pretty intensive homework assignment. Curious about your first sentence, "Vertex matching is a pro/e thing, you can turn it off here." Not sure what pro/e is nor did I see where one might turn it off. Thank you again very much for taking the time to reply.

pro/e is an old CAD system that required you to match the vertices. Modern CAD doesn't really require this any longer.

As a surface is created, keeping it flowing properly and preventing it from bunching up is important and sometimes matching the vertices helps. In your case, your surfaces flow nicely and shouldn't need vertex mapping.

Another thing, as possibly a tip, your primary surfaces that you have defined, can be trimmed back. Then, you can add transition surfaces to connect everything together. This is a standard manifold technique used a lot, at least by me.

So trim your fin back a little bit:

And then add a transition surface between your primary surfaces:

So why would you want this? Because your primary surfaces flow nicely without much curvature. Then, upon transitioning to the other side, you might want tighter curvature. It's hard to control a free flowing surface with tight curvature at it's ends. This is why we have patches and break the manifold into surface patches. Each patch has it's own control.

Unless you want the razor's edge to slice through the water.

This is the bases of surface modeling. Think about the primary surfaces and then the transition surfaces that'll tie it all into a manifold.